(a) Technical Field
The present disclosure relates to a furnace for treating carbon steel with heat, and more particularly to a system for controlling atmospheric gas that is supplied into the furnace.
(b) Background Art
When oxygen flows into a heat treatment furnace or oxygen is generated therein, the oxygen reacts with the carbon steel in the furnace to decarbonize the carbon steel. The decarbonization lowers the dimensional precision of the steel product.
The decarbonization is a phenomenon in which carbon steel reacts with oxygen at a high temperature and the carbon of the carbon steel is removed as CO or CO2 so that the carbon concentration of the steel surface is reduced, thereby transforming the carbon steel to a soft ferrite material.
The decarbonization may lower the hardness of the steel product. It also may generate tensile stress in a surface portion of the carbon steel, causing a deformation thereof or a crack therein. One method to reduce the decarbonization is to supply the heat treatment furnace with an atmospheric gas such as nitrogen and an endothermic gas.
However, when the contents of outside air, oxygen, carbon dioxide, vapor, or sulfur dioxide is higher than that in an equilibrium condition within the furnace while the atmospheric gas is supplied to the furnace, decarbonization occurs therein.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.